%ifndef BOOT_MEMORY_SEGMENTSELECTOR
%define BOOT_MEMORY_SEGMENTSELECTOR
;; 请求特权级（Rest Privilege Level）
;; user mode, kernel mode by default
%define SEGMENT_SELECTOR_RPL_USER  (0b11) 
;; 是否 LDT
%define SEGMENT_SELECTOR_DESCRIPTOR_LDT  (0b1 << 2)
%endif